Autocollimation involves techniques and apparatus of projecting an illuminated target at infinity and receiving the target image after reflection from a flat plane surface for performing a number of different functions. These functions include checking the parallelism of end surfaces of a member, comparing the angle of a work piece to a standard angle member, checking a surface for smoothness or flatness, checking the perpendicularity of surfaces, determining the amount of deflection in precision screws, determining deflection of elastic or springy materials and checking for differences in length between an object and a standard member.
The conventional autocollimator is a single instrument combining the functions of a telescope and a collimator to detect small angular displacements of a mirror surface by means of its collimated light. The device consists of a lens with a reticle rigidly mounted in its focal plane, the reticle being illuminated from the side by a plane reflector or small prism. The reticle usually carries several parallel lines subtending known angles at the lens. An electronic autocollimator provides a continuous output voltage, the sign and amplitude of which are correlated to the angular displacement of the mirror.
Commercial autocollimator devices commonly use a refractive type telescopic system having an ocular eyepiece into which the operator must look. Interpreting the data is therefore subjective. The commercial devices must be set up with expensive angle gauge blocks or master angles and are set up and operated manually.